Magnetic storage medium and magnetic recording apparatus

Abstract

According to one embodiment, a magnetic storage medium includes a plurality of recording layers and a first non-magnetic layer. The plurality of recording layers each includes at least one first magnetic layer and at least one second magnetic layer. The first magnetic layer is made of a first magnetic material which has a first effective perpendicular magnetic anisotropy. Data is stored in first magnetic layer in accordance with a direction of magnetization. The second magnetic layer is made of a second magnetic material having a second effective perpendicular magnetic anisotropy smaller than the first effective perpendicular magnetic anisotropy. First magnetization of the first magnetic layer and second magnetization of the second magnetic layer are in magnetic coupling.

What is claimed is: 
     
         1 . A magnetic storage medium, comprising:
 a plurality of recording layers each including at least one first magnetic layer and at least one second magnetic layer, the first magnetic layer being made of a first magnetic material which has a first effective perpendicular magnetic anisotropy, data being stored in the first magnetic layer in accordance with a direction of magnetization, the second magnetic layer being made of a second magnetic material having a second effective perpendicular magnetic anisotropy smaller than the first effective perpendicular magnetic anisotropy, first magnetization and second magnetization being in magnetic coupling, the first magnetization being magnetization of the first magnetic layer, the second magnetization being magnetization of the second magnetic layer; and   a first non-magnetic layer made of a non-magnetic material and provided between the recording layers.   
     
     
         2 . The medium according to  claim 1 , wherein the first magnetization and the second magnetization are in ferromagnetic coupling. 
     
     
         3 . The medium according to  claim 1 , wherein the first magnetization and the second magnetization are in antiferromagnetic coupling, the antiferromagnetic coupling indicating that directions of magnetization are opposite to each other. 
     
     
         4 . The medium according to  claim 1 , further comprising a second non-magnetic layer made of a non-magnetic material and provided between the first magnetic layer and the second magnetic layer, wherein
 the first magnetization and the second magnetization are coupled with each other by magnetostatic effect and magnetic exchange coupling via the second non-magnetic layer.   
     
     
         5 . The medium according to  claim 1 , wherein the first magnetization and the second magnetization are coupled with each other by magnetostatic effect and magnetic exchange coupling caused by direct coupling of the first magnetic layer and the second magnetic layer. 
     
     
         6 . The medium according to  claim 1 , wherein the first magnetic layer and the second magnetic layer are stacked alternately. 
     
     
         7 . The medium according to  claim 1 , wherein the recording layer includes two of the first magnetic layers and one second magnetic layer is interleaved between the two of the first magnetic layers. 
     
     
         8 . The medium according to  claim 1 , wherein coercivity of the second magnetic layer is smaller than the coupling magnetic field between the first magnetic layer and the second magnetic layer. 
     
     
         9 . The medium according to  claim 1 , wherein the first magnetic layer has effective perpendicular magnetic anisotropy of 2 Merg/cm3 or more, and the second magnetic layer has a ferromagnetic resonance frequency of 10 GHz or less. 
     
     
         10 . A magnetic recording apparatus, comprising: the magnetic storage medium of  claim 1 ; and a read head.